The invention relates to racket stringing apparatus or machines used for emplacement and tensioning of strings in racket heads, e.g., tennis rackets and the like, and more particularly to devices for aiding in the installation and tensioning of the racket head cross strings.
Racket heads are customarily strung with main strings running longitudinally of the racket parallel to the handle and perpendicularly related cross strings which are woven through the longitudinal strings. In the preferred stringing of a racket, the main or longitudinal strings are first installed and tensioned. Since this is done in the absence of the cross strings, the main strings will be automatically drawn without interference into straight lines across the racket head. The cross strings are then installed by weaving each cross string over and under alternate main strings, the cross string being thus drawn in a sinuous path. As the cross string is tensioned it is pulled into a straighter line and at the same time deflects the main string from its straight line into a sinuous form. The interaction of the main and cross strings upon pulling through and tensioning of the latter has several dilatorious effects. The frictional rubbing of the strings against each other may cause "burning" and consequent weakening of the strings. Secondly and very importantly, it has been found that in the conventional placement and tensioning of the strings as above described it is virtually impossible to obtain a uniformity of tensioning of the cross strings.
Various devices have been proposed to facilitate the placing of the cross strings by engaging and displacing in opposite directions, perpendicularly to the plane of the racket head, alternate main strings so as to open a clear lateral path across the racket head for threading into position and tensioning a cross string. Examples are devices made or distributed by Mosler Mfg. Co. of Los Angeles, Calif.; Holland Products of Lancaster, Pa.; and Sports Pal Co. Inc. of St. Louis, Mo.
Devices heretofore available for assisting in the placing and tensioning of the cross strings in a racket head have not found wide acceptance. They have been awkward and slow to use. Consequently, conventional racket stringing is done in the main without the benefit of a cross-stringing aid.